Kuler was an application we've seen before and was released on labs last year. It is mentioned as the first of many Rich Internet Applications coming and it sounds like these RIAs will tie very closely into Creative Suite 3, due out later this year.
Kuler is meant as a designer tool that will easily allow both color discovery and thematic color. Kuler allows you to create color themes which you can import into Photoshop, Illustrator and other Adobe products. You can share these color swatches and download versions created by other users. Because I'm not a designer, it's fun to play with, but I don't know how I would use it. The toolset seems powerful though. While building color swatches you can choose from a variety of rules which adjust the connections between colors as they are positioned on the color wheel.
The Kuler team has created an apple dashboard widget that ties into Kuler and lets you browse created styles. You can go back to the theme on the site or copy the hex values to the clipboard for use anywhere. They also demoed integration with Illustrator so you can browse Kuler themes directly from Illustrator and customize what themes display using RSS feeds. Then it's just a one click process to take that theme from Kuler into Illustrator. I pretty seamless workflow for designers using user generated content. That same workflow can be used to push content from Illustrator to Kuler linking the desktop and the web.